An exemplary prior art image forming apparatus of this type is configured as shown in FIG. 6.
The prior art system uses an endless organic photoconductive (OPC) belt 1 as a sensitized member. The OPC belt 1 is supported by small rollers 2, 2, large roller 3 and driving roller 4 all located at the back thereof, and is driven by the driving roller 4 in an arrow-marked direction in FIG. 6. Various components are located around the OPC belt 1 to form an image on paper or other recording medium. More specifically, one surface of the OPC belt 1 is electrified with an even positive potential by a corona charging operation of an electrifier 5. Subsequently, a photographic writing unit 6 writes an electrostatic latent image exhibiting a print pattern on the OPC belt 1, and a developing unit 7 forms a toner image on the OPC belt 1 by selectively depositing negative-electrified toner to the electrostatic latent image. When the toner image reaches a transfer unit 8 as the OPC belt 1 travels, an electrostatic attraction force of the transfer unit 8 causes the toner image to be transferred from the OPC belt 1 to a sheet of paper 9 to form a final image thereon. After this, the paper 9 is detached from the OPC belt 1 and transported to a fixing unit 10 which fixes the toner image on the paper 9 under a certain heat or pressure. The paper 9 is subsequently discharged to a discharge tray (not shown). The OPC belt 1, passing through the transfer unit 8, is cared of by a deelectrifier 11 to remove a residual charge therefrom and by a cleaner 12 to remove residual toner therefrom.
In the prior art system, however, although the electrostatic latent image written on the OPC belt 1 by the photographic writing unit 6 is formed under an excellent high resolution, the toner often adheres to the OPC belt 1 other than the electrostatic latent image thereon, resulting in a low resolution toner image on the OPC belt 1 and a low resolution final image on the paper 9. That is, it often provides a low printing quality.
In order to improve the resolution in development by the developing unit 7, a strict control is required about the bias voltage of the developing unit 7, electrification degree of the toner, the gap between the developing unit 7 and the OPC belt 1, etc., and this invites a complicated structure of the system and requires a careful maintenance.
Additionally, around the OPC belt 1 must be provided a lot of parts or members such as photographic writing unit 6, developing unit 7, transfer unit 8, deelectrifier 11 and cleaner 12, and they invite a complicated, large-scaled structure of the entire system.